The subject invention relates to devices for measuring characteristics of an object's motion through a predetermined zone, and particularly to highly accurate, high-speed time trap devices, which are adapted for use as training aids in sporting type activities or for use in evaluating sporting equipment. Such applications include, for example, training devices for golf, tennis, baseball, football, squash, soccer, volleyball, bowling, boxing, and karate, wherein speed and acceleration characteristics of an object's motion, such as for a club, racket, ball, foot, or hand, are displayed as an aid in performance evaluation.
Systems which employ pulsed, infrared beams to measure elapsed time between interruptions of the beams are known in the art. For example, U.S. Pat. No. 3,932,746 describes an elapsed time meter which incorporates pulsed, infrared beams to monitor remotely located start and stop gates which would seem to be widely separated and arbitrarily employed. Also, in said system, the pulsing of the beams (the audio frequency range is recommended therein) appears to be for the purpose of improving the receiver's signal to noise ratio and for alignment, and not as a primary factor in establishing the measurement accuracy of the system. Although the just referenced and similar type systems may be quite satisfactory for their intended purposes, e.g. timing skiing events, a significant aspect of the subject invention is the recognition that there exists a wide range of applications which require low cost, highly accurate, and reliable systems for measuring the speed and/or acceleration of high speed objects over a very short distance of interest, e.g. the motion of a golf club, ball bat, or foot as it approaches contact with the ball.
Other prior art devices, such as the velocity meter disclosed in U.S. Pat. No. 3,685,909, relate to systems wherein a pair of parallel, non-pulsed, visible light beams is used to provide beam interruption data to analog circuits which produce a meter indication of the velocity of a golf clubhead as it passes through the beams. Since no finite time increments are encoded on the non-pulsed beams, the accuracy of this type of velocity meter would seem to be dependent on the varying characteristics of the analog circuits employed. U.S. Pat. Nos. 2,571,974; 2,825,569; 2,933,681; 3,020,049; and 3,601,408 are representative of the historical development of the art of golf training devices. U.S. Pat. No. 3,373,612 discloses a mechanical golfer for testing balls; U.S. Pat. No. 3,117,451 describes a photoelectric baseball batter's swing analyzer, and U.S. Pat. No. 3,016,812 illustrates a motion analyzer which relates to bowling activities. As will become evident from the following description, these devices do not provide the accuracy, versatility, reliability, and economy available from systems employing the features of the subject invention.